If methane hydrate allows much of the world to switch from oil to gas, the conversion would undermine governments that depend on oil revenues, especially petro-autocracies like Russia, Iran, Venezuela, Iraq, Kuwait, and Saudi Arabia. Unless oil states are exceptionally well run, a gush of petroleum revenues can actually weaken their economies by crowding out other business. Worse, most oil nations are so corrupt that social scientists argue over whether there is an inherent bond-a "resource curse"-between big petroleum deposits and political malfeasance. It seems safe to say that few Americans would be upset if a plunge in demand eliminated these countries' hold over the U.S. economy. But those same people might not relish the global instability -- a belt of financial and political turmoil from Venezuela to Turkmenistan -- that their collapse could well unleash.

On a broader level still, cheap, plentiful natural gas throws a wrench into efforts to combat climate change. Avoiding the worst effects of climate change, scientists increasingly believe, will require "a complete phase-out of carbon emissions... over 50 years," in the words of one widely touted scientific estimate that appeared in January. A big, necessary step toward that goal is moving away from coal, still the second-most-important energy source worldwide. Natural gas burns so much cleaner than coal that converting power plants from coal to gas-a switch promoted by the deluge of gas from fracking-has already reduced U.S. greenhouse-gas emissions to their lowest levels since Newt Gingrich's heyday.